Creating backspace on iOS calculator

Question

I'm trying to add a backspace button to remove the last entered digit in a calculator, but I can't seem to get it. Here is what I've tried:

-(IBAction)backspacePressed:(UIButton *)sender {

    NSMutableString *string = (NSMutableString*)[display text];

    int length = [string length];

    NSString *temp = [string substringFromIndex:length-1];

    [display setText:[NSString stringWithFormat:@"%@",temp]];

}

Any ideas?

what if the last was not a digit? what if it is an operand? – lakshmen Feb 04 '12 at 20:15 — lakshmen, Feb 04 '12 at 20:15

score 3 · Answer 1 · answered Jul 06 '11 at 04:30

3

I think you want [string substringToIndex:length-1] instead of [string substringFromIndex:length-1].

answered Jul 06 '11 at 04:30

Dr. Acula

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@Jason He want to delete the last character, not the first one – KingofBliss Jul 06 '11 at 04:34
My mistake, I must have misread the question. Comment deleted. – titaniumdecoy Jul 06 '11 at 04:36

score 1 · Answer 2 · answered Jul 06 '11 at 04:30

1

Use subStringToIndex method instead of subStringFromIndex

NSString *temp = [string substringToIndex:length-1];

answered Jul 06 '11 at 04:30

KingofBliss

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+1 for editing the post AND getting the right answer in within 20 seconds of the other guy :) – Steve Jul 06 '11 at 04:31

Creating backspace on iOS calculator

2 Answers2

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